<script>
function clearText(thefield){
if (thefield.defaultValue==thefield.value)
thefield.value = ""
} 
</script>
<form method="get" id="searchform" action="<?php echo esc_url( home_url( '/' ) ); ?>">
		<input type="text" class="search_txt" name="s" id="s" value="Пошук товарів..."  onFocus="clearText(this)" />
		<input type="image" class="submit" src="<?php echo get_template_directory_uri(); ?>/img/search_icon.png">
</form>